Prior Art FIG. 1 illustrates a method 100 of manufacturing a conventional tape head for a linear tape drive. As shown, in operation 102, a plurality of “quads” is cut from a wafer, which may be further cut into “mini-quads.” Thereafter, a plurality of closures is bonded to the mini-quads. See operation 104. Next, in operation 106, the closures are ground and an extender bond operation is performed. At this point, in operation 108, an air bearing surface (ABS) is lapped, after which the mini-quad is sliced to provide a plurality of “rows” each with a planar ABS.
With continuing reference to FIG. 1, a back portion of each row is lapped and inspected. See operation 110. The rows are then subjected to a magnetic test in operation 112, followed by additional inspections and measurements in operation 114. It is at this time that the rows are trimmed to afford “chiplets” and cleaned in operation 116.
To provide the clean “chiplets” with support, they are bonded to U-beams in operation 118 and again inspected and measured in operation 120. A taper-less grind is then carried out in operation 122 to notch a portion of each head. Such taper-less grind is carried out in order to reduce the area on which a tape passes during use. By doing so, the tape is guided over the head in an optimal manner.
Finally, in operations 124–128, a magnetoresistive profile of each head is enhanced and again inspected and measured, after which a final cleaning operation is performed. More information regarding a number of the foregoing operations will be set forth with reference to the following figures.
Prior art FIG. 2 illustrates a mini-quad 200 of heads 202 that have been cut from a wafer, in accordance with operation 102 of FIG. 1. As shown, the mini-quad 200 includes two columns of multiple rows of heads 202. During the fabrication of the mini-quad 200, an array of heads 202 including read and write elements, auxiliary circuits, pads 204 coupled to the elements, and pads 206 coupled to the auxiliary circuits are fabricated on a common substrate in a deposition of metallic and non-metallic layers. The auxiliary circuits are sometimes referred to as electrical lap guides (ELGs), and are currently positioned away from the elements towards opposite ends of the head 202. Patterning of the array of elements, ELGs, pads, and connections therebetween is accomplished using photolithography in combination with etching and lift-off processes. During lapping of operation 110 (FIG. 1), the pads 206 are attached to a resistance measuring device that determines an extent of the lapping based on a change in resistance of the ELGs. Note that the pads 206 are much larger than pads 204. This is because the connection to the resistance measuring device is not a permanent connection, but is rather accomplished using a biased pin or similar coupling mechanism.
Prior art FIG. 3 illustrates a mini-quad 300 including a plurality of strips of closures 302 attached thereto, in accordance with operations 104 and 106 of FIG. 1. Such closures 302 define a plurality of slots 304 in which the pads 206 associated with the ELGs reside. Such closures 302 have recently become a common part of wafer processing in view of the benefits they afford in resultant heads. More information on the manufacture and use of closures 302 and the related benefits may be found with reference to U.S. Pat. Nos. 5,883,770 and 5,905,613 which are incorporated herein by reference in their entirety.
Prior art FIG. 4 illustrates a head 400 after the lapping and tests of operations 108–114, the trimming of operation 116 and the attachment of the U-beam of operation 118 of FIG. 1. To conserve wafer utilization, the head 400 is extremely thin in shape and form. The elements 406 are positioned towards the middle of the head 400 and the ELGs 408 are positioned towards opposite ends of the head 400. In order to increase the stability of the head 400 for the suitable use thereof, the head 400 is attached to a beam 404 of some sort formed of a rigid material. Such beams 404 are often referred to as a “U-beams.” Again, the closure 402 is shown in FIG. 4.
Prior art FIG. 5 illustrates a head 500 after the taper-less grind of operation 122 of FIG. 1. Such taper-less grind renders a notch 502 which allows a proper wrap angle of a tape as it moves over an ABS 504 of the head 500 during use.
Prior art FIG. 6 illustrates the coupling of two heads 500 of FIG. 5 in use. Specifically, in FIG. 6, two heads 500 are mounted on U-beams 404 which are, in turn, adhesively coupled. Cables 602 are fixedly coupled to the pads 204. The tape 604 wraps over the heads 500 at a predetermined wrap angle α.
As shown, FIG. 6 illustrates the head 500 for a read-while-write bidirectional linear tape drive. “Read-while-write” means that the read element follows behind the write element. This arrangement allows the data just written by the write element to be immediately checked for accuracy and true recording by the following read element.
As mentioned above, during head fabrication, the head is lapped down to its designed stripe height. In order for the lapping tool to know when it has reached its targeted stripe height, the prior art method measures the resistance of the ELGs placed at the top and bottom ends of the head, fairly distant from the active read and write elements. However, due to variations in head surface geometry and instabilities inherent in the lapping process, the center active read and write elements are not lapped accurately to the targeted stripe height and throat height. Based on the current track sizes, these inaccuracies are still acceptable. However, as tracks become smaller and smaller, and tolerances for the target stripe height become tighter and tighter, a new solution is required.
One solution would be to use the read elements as the lapping guides. However, the pads 204 coupled to the read elements are too small to make reliable contact with the contacts of the resistance measuring device. The contacts of the resistance measuring device are not fixedly attached to the pads but are typically biased pins that rely on friction for maintaining contact. The lapping process is rough and can cause the module to shift or vibrate, which in turn creates a tendency of the contacts to shift and lose contact with the pads 204. Compounding the problem, the contacts of the resistance measuring device are typically larger than the pads 204, and therefore can contact adjacent pads 204, creating a short.
Because of these problems, standard practice is to place the ELGs on the outer ends of the module and only uses those as lapping guides. The ELGs are coupled to the large pads 206 positioned outside the pads 204 due to the small available area for pad placement. The extent of lapping at the ends of the head can be accurately determined by the changing resistance through the ELGs. What cannot be accurately measured, however, is the extent of lapping in the middle of the head, i.e., between the ELGs. Current tape modules are 22 mm in length. However, the elements only span about 3 mm, meaning that the lapping measurements are taken very far away from the active area of the head. Tolerances are in microns, and are very sensitive, so it becomes harder to lap within the tolerances, and will become harder as the stripe heights of the elements become smaller in future generations of heads.
What is thus needed is a solution for reliable lapping that is also capable of achieving a tight stripe height and throat height tolerance for a magneto-resistive head.